Ventilation systems such as ventilation systems with energy recovery require airtight enclosures for accommodating the ventilation system. If the enclosure is not airtight but has leaks air may be drawn into the system or escape from the system through leaks in the enclosure whereby the efficiency of the system will be reduced. Leaked air may cause undesired effects on the functionality of the unit, e.g. due to increased energy use for air transport, pressure imbalance in ventilated rooms, decreased efficiency of energy recovery, incorrect measurements by internal sensors and ensuing control errors, formation of condensate in critical parts of the unit, and whistling or hissing noises.
Components and modules of a system according to the invention will typically be accommodated in an enclosure composed of two or more enclosure shells that are assembled along mating edges to form a closed airtight enclosure. Preferred materials for the enclosure shells are expanded polypropylene, EPP, and expanded polystyrene, EPS. Systems for domestic use may be accommodated in enclosures well above one meter in a long direction, while dimensions in a short direction can be a few tens of centimeters. With rectangular enclosures this means that long edges of the shells are separated by a distance corresponding to the length of the short edges, while short edges of the shells are separated by a distance corresponding to the length of the long edges. Manufacturing tolerances are mainly proportional to dimensions, and since the long edges of the shells are a relatively short distance apart, this in turn means that the distance between opposed long edges of a shell is manufactured to relatively small tolerances, and further, since the short edges of the shells are a relatively long distance apart, this in turn means that the distance between opposed short edges of a shell is manufactured to relatively large tolerances. This difference in tolerances results in correspondingly different requirements to the mating surfaces of edges to be joined in order to ensure an airtight enclosure when the shells have been assembled.
It is therefore desirable to have an enclosure to be assembled from two or more enclosure parts or enclosure shells to form an airtight enclosure where tolerances are absorbed in the structure of the enclosure parts themselves without having to add supplementary tightening material and without any need of additional tooling of the shells. Furthermore, it is desirable that the combined shells are self-supporting without any need for gluing the parts permanently together, and that it is possible to disassemble and reassemble the parts non-destructively and without loss of performance in case of modification or maintenance and repair of the system.